EXHIBIT 99.1 PRESS RELEASE May 9, 2024 Arrowhead Pharmaceuticals Reports Fiscal 2024 Second Quarter Results – Conference Call and Webcast Today, May 9, 2024 at 4:30 p.m. ET PASADENA, Calif., May 9, 2024 — Arrowhead Pharmaceuticals, Inc. (NASDAQ: ARWR) today announced financial results for its fiscal 2024 second quarter ended March 31, 2024. The Company is hosting a conference call today, May 9, 2024, at 4:30 p.m. ET to discuss the results. Christopher Anzalone, Ph.D., President and CEO at Arrowhead, said: “ ...